Step 1
Whisk flour baking powder salt ground ginger cinnamon nutmeg and cayenne together in a bowl until thoroughly combined.
Step 2
Combine butter brown sugar and molasses in a bowl; mix with a spatula until creamy. Whisk in eggs one at a time until smooth. Add vanilla and chopped ginger. Mix and mash with the whisk until ginger is evenly distributed and coated with the butter-sugar mixture about 1 minute.
Step 3
Mix in 1/2 of the dry ingredients with a spatula until incorporated. Mix in remaining dry ingredients until dough is very wet and sticky.
Step 4
Transfer dough to a long piece of plastic wrap using a buttered knife to help if necessary. Wrap plastic around the dough and shape with your hands into a uniform log about 12 to 14 inches long by 2 1/2 inches wide. Place in the refrigerator to chill for at least 30 minutes.
Step 5
Preheat the oven to 350 degrees F (175 degrees C). Line a baking sheet with a silicone baking mat.
Step 6
Remove dough from the refrigerator unwrap and place on the prepared baking sheet. Wet your fingers and smooth out any edges.
Step 7
Bake in the center of the preheated oven until a toothpick inserted into the center comes out clean about 30 minutes.
Step 8
Remove loaf from the oven cover with a clean towel and let sit for 20 minutes. Reduce oven temperature to 325 degrees F (165 degrees C).
Step 9
Uncover the loaf and brush a little water around the bottom edge to soften. Transfer to a cutting board.
Step 9
Use a serrated knife to cut the loaf into 1/2-inch slices. Cut at an angle for longer biscotti or straight across for shorter ones. Transfer slices back to the baking sheet.